However, firefighters and rescue operations quickly arrived at the accident site, the Governor added.
Turkish National Defense Ministry, Milli Savunma Bakanlığı, also confirmed the death toll on its official Twitter handle and said that an investigation into the matter was initiated.
Our UH-1 type helicopter from Istanbul / 4th Land Aviation Regiment Command has suffered an accident in Çekmekoy for an unknown reason. In the accident, 4 heroic gunmen were martyred. An investigation into the incident was initiated, the Ministry said.
We extend our condolences to the saintly martyrs and to our noble nation.
The Presidency of the Board of Inspectors of the Ministry of National Defense has been appointed to examine the helicopter crash in Istanbul where four of our heroic comrades were killed. Following the comprehensive review, the result will be shared with the public, the Ministry added.
Turkish Parliament Speaker, Binali Yildirim, also expressed sadness and extended condolences to the families of the martyred soldiers on Twitter.
I wish God's mercy from the Mehmet the Lord, I wish the families of martyrs, the Speaker said.